JPH08144762A - Direct injection type spark ignition internal combustion engine - Google Patents

Abstract

PURPOSE: To quickly realize stratification of air-fuel mixture by supplying fuel into a combustion chamber while preventing a fuel droplet from adhering to a piston or the like and forming a wall flow. CONSTITUTION: A fuel injection valve 10 disposed on the lower side of a cylinder head 2 injects fuel through a pair of jet orifices obliquely bored on the forward end side thereof when it reaches the vicinity of ignition timing. Fuel jetted from one jet orifice and fuel from the other jet orifice collide with each other to be atomized and form flat fuel spray F which is substantially horizontal to the crown surface 3A of a piston 3 and spread substantially fan-like. The flat fuel spray F is quickly gasified to form air-fuel mixture. The air-fuel mixture is pushed up to the spark plug 9 side by the piston 3 to realize stratification.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection type spark ignition internal combustion engine in which fuel injected into a combustion chamber is ignited by a spark plug.

[0002]

2. Description of the Related Art A direct injection type spark ignition internal combustion engine in which fuel is directly injected into a combustion chamber to form a mixture and the mixture is forcedly ignited by a spark plug is disclosed in, for example, Japanese Patent Laid-Open No. 63-63. -215817 and the like.

Therefore, a direct injection type spark ignition type internal combustion engine of this type according to the prior art is disclosed in Japanese Patent Laid-Open No. 63-2158.
Taking the example described in Japanese Patent Publication No. 17 as an example, description will be made with reference to FIG.

The upper end of the cylinder 100 is covered by a cylinder head 101, and a combustion chamber 103 is defined between the piston 102 and the cylinder head 101 provided in the cylinder 100. Also, the cylinder head 1
In 01, an intake passage 104 and an exhaust passage 105 are formed, and these intake passages 104, 105 and the combustion chamber 103 are connected via an intake valve 106 and an exhaust valve 107.

The spark plug 108 is provided on the cylinder head 101 so as to correspond to substantially the center of the cylinder 100, and the fuel injection valve 109 is provided on the cylinder 100 so that the spark plug 108 is oriented.

The direct injection type spark ignition type internal combustion engine according to the prior art has a structure as described above, and the piston 10
When 2 rises and reaches the vicinity of the top dead center, the fuel injection valve 109
Injects the fuel that spreads in a conical shape toward the electrode portion of the spark plug 108. Then, this injected fuel is vaporized in the vicinity of the spark plug 108 to form an air-fuel mixture, and the air-fuel mixture is spark plug 1
It is ignited by 08.

[0007]

By the way, in the above-mentioned prior art, by injecting fuel toward the spark plug 108, a mixture is formed in the vicinity of the spark plug 108, and lean burn (lean burn) is performed. ) Attempts to realize the stratification of the air-fuel mixture (stratified combustion) that is necessary at times. However, since the fuel is injected toward the spark plug 108, the fuel droplets are likely to adhere to the electrode portion of the spark plug 108, the wall surface of the cylinder head 101, and the like. In particular, the amount of fuel that collides with and adheres to the spark plug 108 and the cylinder head 101 is likely to increase during high-load running in which the engine required fuel increases. Therefore, the spark plug 1
In 08, phenomena such as "fog" and "smolder" occurred,
In addition to the possibility of causing ignition mistakes, the fuel adhering to the wall surface of the cylinder head 101 becomes a wall flow, which may worsen the exhaust emission of HC and the like.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to realize stratified charge combustion while preventing injection fuel from adhering to spark plugs, cylinder heads and the like to form a wall flow. An object is to provide a direct injection type spark ignition type internal combustion engine that is made possible.

[0009]

Therefore, the structure adopted in the direct injection type spark ignition internal combustion engine according to the present invention is a fuel injection valve for injecting fuel into a combustion chamber formed between a cylinder head and a piston. And a spark plug ignition engine for igniting an air-fuel mixture formed in the combustion chamber, wherein the fuel injection valve has a flat fuel spray near the ignition timing. The feature is that the injection is performed substantially horizontally with respect to the crown surface of the piston.

The fuel injection valve includes an injection valve body,
A pair of injection holes formed on the tip side of the injection valve main body, and the injection holes are formed so that the line connecting the centers of the outlets of the injection holes is substantially perpendicular to the crown surface of the piston. It is preferable that the injection axes of the injection holes are set so that the injected fuels collide with each other in the combustion chamber.

Further, it is more preferable that the fuel injection valve is set so that the ratio of the square roots of the cross-sectional areas of the outlets of the respective injection holes is in the range of 1.25 to 3.50.

[0012]

When the flat fuel spray is injected substantially horizontally to the crown surface of the piston in the vicinity of the ignition timing, the piston crown surface and the cylinder are kept in an atmosphere in which the temperature of the compressed air is rising. Fuel can be fed into the combustion chamber substantially without impacting any of the heads. The supplied fuel spray is pushed up toward the cylinder head while vaporization progresses as the piston rises, so that a mixture is formed in the vicinity of the spark plug, and stratification of this mixture is maintained until ignition. .

Further, the fuel injection valve comprises an injection valve main body and a pair of injection holes formed at the tip end side of the injection valve main body, and a line connecting the centers of the outlets of the respective injection holes with respect to the crown surface of the piston. By arranging the injection holes so that they are substantially vertical, and setting the injection axis of each injection hole so that the injected fuel collides with each other in the combustion chamber, atomized, flat and thin fuel spray is applied to the piston crown. It is possible to jet almost horizontally to the surface.

Furthermore, if the fuel injection valve is set so that the ratio of the square root of the cross-sectional area of the outlet of each injection hole is in the range of 1.25 to 3.50, the fuel injected from each injection hole is When a collision occurs, a strong resonance phenomenon can be obtained while ensuring a collision area, and atomization can be further promoted.

[0015]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 is a structural explanatory view showing a main part of a direct injection type spark ignition type internal combustion engine according to an embodiment of the present invention.
A plurality of cylinders 1 (only one is shown) are provided, and the upper opening of each cylinder 1 is airtightly covered by a cylinder head 2. A piston 3 is slidably provided in the cylinder 1, and between the crown surface 3A of the piston 3 and the cylinder head 2, a substantially conical or triangular upper volume portion 4A and a substantially columnar shape are formed. Lower volume part 4B
And a four-valve pentroof type combustion chamber 4 is defined. Note that the combustion chamber is not limited to this, and may be another type of combustion chamber such as a hemisphere.

The cylinder head 2 is provided with an intake passage 5 and an exhaust passage 6 facing each other.
The exhaust passage 6 has a bifurcated intake port 5
A, and communicates with the combustion chamber 4 via the exhaust port 6A.
The intake port 5A and the exhaust port 6A are
The intake valve 7 and the exhaust valve 8 driven by a valve mechanism (not shown) are opened and closed.

The spark plug 9 is provided on the cylinder head 2 so as to correspond to substantially the center of the cylinder 1, and the tip end side thereof is located in the combustion chamber 4.
Facing inside (only the electrode portion of the spark plug 9 is shown). The spark plug 9 generates a spark by being supplied with electric power by an ignition device (not shown) and ignites the air-fuel mixture.

The fuel injection valve 10 is located near the cylinder 1 and is provided below the cylinder head 2.
As shown in the plan view of FIG. 1, a flat fan-shaped fuel spray is injected substantially horizontally to the crown surface 3A of the piston 3.
That is, in the fuel injection valve 10 according to the present embodiment, as shown in the partial sectional view of FIG. 3, a relatively thin, flat fuel spray is applied to both the wall surface of the cylinder head 2 and the crown surface 3A of the piston 3. The injection is performed substantially horizontally toward the inner wall of the opposing cylinder 1 while ensuring the clearance.

Next, the structure of the fuel injection valve 10 will be described in detail with reference to FIGS. 4 and 5. FIG. 4 is an enlarged cross-sectional view showing a main part of the fuel injection valve 10, in which a stepped tubular casing 12 forming a part of the injection valve body 11 has an electromagnetic actuator 13 including a coil or the like. Is attached via a yoke 14, and a core 15 formed of a magnetic material in a substantially cylindrical shape is provided in the hollow portion on the inner peripheral side of the electromagnetic actuator 13.

The valve body 16 is formed of a magnetic material into a substantially hemispherical shape, and is disposed inside the casing 2. This valve body 16
A plurality of elastic thin support parts 1 are provided on the outer periphery of the base end side of the
6A is formed integrally by projecting outward in the radial direction, and the end portions of each of the support portions 16A have a yoke 14 and a casing 1.
It is pinched and fixed between the two. In addition, this valve body 16
Is always biased in the valve closing direction by the coil spring 17 and the leaf spring 18, and when the electromagnetic actuator 13 is excited to generate a suction force, the valve is opened against the spring force. It has become.

On one end side (tip side) of the casing 12,
A valve seat portion 19 for seating the valve body 16 is formed so as to project inward in the radial direction. When the valve body 16 is seated on the valve seat portion 19, the injection hole 19A is closed and the fuel supply pipe A fuel pool 20 in which fuel from (not shown) is pooled is separated from a nozzle member 21 described later.

The nozzle member 21 is liquid-tightly mounted by covering one end side of the casing 12, and one injection hole 22 and the other injection hole 23 having different diameters are obliquely formed.

That is, as shown in FIG. 5, the outlet 22A of one of the injection holes 22 is formed in a large elliptical shape having a major axis dimension DL ₁ and a minor axis dimension DS ₁ , and its axis X ₁ -X.
₁ is provided so as to be inclined by a predetermined angle θ _{1 with} respect to the axis O-O of the fuel injection valve 10. The outlet portion 23A of the other injection hole 23 is formed in a small elliptical shape having a major axis dimension DL ₂ and a minor axis dimension DS ₂ , and its axis X ₂ -X.
₂ is formed so as to be inclined at a predetermined angle θ _{2 with} respect to the axis O-O. Here, the axis O-O of the fuel injection valve 10 substantially coincides with the opening / closing direction of the valve body 16 and is parallel to the crown surface 3A of the piston 3. Further, for the reason described below, the line C-C connecting the axial centers of the injection holes 22 and 23 is
It is perpendicular to a line H-H parallel to the crown surface 3A of the piston 3.

Then, the injection axis X of each of the injection holes 22 and 23
_1- X ₁ and X ₂ -X ₂ intersect at a point CP on the axis O-O,
At the intersection CP, the fuel injected from the injection holes 22 and 23 collides with each other. The injection axis lines X ₁ -X ₁ and X ₂ -X ₂ do not intersect at one point on the same plane,
It is also possible to provide the injection holes 22 and 23 so that the ejected liquids may collide with each other even when there is an axial distance.

Here, each of the injection holes 22 and 23 has a ratio α (α = (S ₁ ) ^1/2 / (S ₂ ) of the positive square roots of the cross-sectional areas S ₁ and S ₂ of the outlet portions 22A and 23A. ) ^1/2 ) is set to a value within the range of "1.25 to 3.50" for the reason described later.

Next, in making the present invention, the ratio of the square root of the cross-sectional area of the outlet portions 22A, 23A of the respective injection holes 22, 23 (hereinafter referred to as the "aperture ratio α") and the resonance are uniquely found. Relationships and the like will be described with reference to FIG.

That is, FIG. 6 is a characteristic diagram showing the relationship between the aperture ratio α and the resonance phenomenon which is a non-linear pull-in phenomenon.
It was found that changing the aperture ratio α in the range of 1 to 4.5 causes a non-linear change in the resonance strength generated at the time of collision. Specifically, when the aperture ratio α is increased to “1.25”, the resonance strength is increased to a level equal to or higher than that of the conventional technique, and when the aperture ratio α is “about 1.5”, the resonance strength is increased. Reaches maximum level. When the aperture ratio α is further increased, the strength of resonance gradually decreases, and the aperture ratio α becomes “3.5”.
Then, the strength of resonance is again at the same level as in the prior art.

Therefore, the aperture ratio α is set to "1.25-3.5.
It can be understood that if the value is set to "0", stronger resonance can be obtained than in the conventional technique, and atomization of fuel can be achieved by utilizing this strong resonance phenomenon.

On the other hand, FIG. 7 shows the uniquely found aperture ratio α
FIG. 3 is a characteristic diagram showing the relationship between the fuel collision area and the fuel collision area. When the aperture ratio α is increased from “1”, the ratio of the fuel collision area decreases quadratically and exponentially. To do. That is, when the aperture ratio α exceeds “3.5”, the area ratio of the non-collision portion increases (about 90% or more), one spray penetrates the other, and atomization does not occur.

Therefore, even if the aperture ratio α is set to exceed "3.5", a stronger resonance than that when the aperture ratio α is "1" is not obtained, atomization cannot be achieved, and the fuel is Since the ratio of the collision area is reduced to β ₂ , the total amount of atomized fuel obtained as a synergistic effect of the both decreases as a result. On the other hand, when the aperture ratio α is “1.25”, the collision area ratio takes a slightly low value β ₁ , but the reduction rate is small.

Therefore, in the present invention, the value of the aperture ratio α is
It is preferably in the range of “1.25 to 3.50”.

Next, the operation of this embodiment having such a configuration will be described. First, the control unit
When it is detected that the ignition timing has been reached based on an output signal from a crank angle sensor (not shown), a control signal is output to the electromagnetic actuator 13 for excitation. Then, when the electromagnetic actuator 13 sucks the valve element 16 through the core 15, the fuel in the fuel reservoir 20 flows into the injection holes 22 and 23 through the injection hole 19A of the valve seat portion 19, and the injection holes 22 and 23 are injected. It is injected into the combustion chamber 4 via 22 and 23, respectively. Here, "near the ignition timing" means a predetermined period before the ignition timing close to the compression top dead center, and since the piston 3 has risen to near the top dead center near this ignition timing, the compressed air Temperature is high.

The fuel injected from the fuel injection valve 10 joins at the intersection CP where the axes O--O, X ₁ --X ₁ and X ₂ --X ₂ intersect, and collides with each other from an oblique direction. It is atomized by the strong resonance phenomenon. Here, the fuel injected from each of the injection holes 22 and 23 collides with each other and is atomized, so the atomized fuel is injected along the direction of the combined vector of the injected fuels, and the atomization shape is As shown in FIGS. 1, 3 and 4, it has a flat and substantially fan shape.

That is, since the injected fuels collide with each other from an oblique direction, the forces applied in the oblique direction (axis X ₁ -X ₁ direction or axis X ₂ -X ₂ direction) given at the time of injection are canceled, Thus, the flat fuel spray F spreading in a substantially fan shape is formed. Therefore, the outlet portion 22 of each injection hole 22, 23
Since the line C-C connecting the centers of A and 23A and the direction in which the fuel spray F is flattened are orthogonal to each other, the direction in which the fuel spray F is flattened is set in the present embodiment. In order to be parallel (horizontal) to the crown surface 3A of the piston 3,
The injection valve body 1 is so arranged that the line C-C connecting the centers of the outlet portions 22A and 23A is perpendicular to the crown surface 3A of the piston 3.
Has been arranged.

However, since it is not necessary to obtain a geometrically strict parallel relationship or a horizontal relationship, the direction in which the fuel spray F is flattened is substantially parallel to the crown surface 3A of the piston 3. , Horizontal relationship is enough. Further, since the cylinder head 2 normally projects upward in the axial direction of the cylinder 1 (top dead center direction) or is parallel to the horizontal cross section of the cylinder 1, the fuel spray F is applied to the crown surface 3A of the piston 3. That is, the fuel spray F does not substantially collide with the cylinder head 2 as well.

The flat fuel spray F that spreads out in a substantially fan shape
Moves in the high temperature compressed air toward the wall surface of the opposing cylinder 1 while ensuring the clearance from both the crown surface 3A of the piston 3 and the wall surface of the cylinder head 2, and during this time, it vaporizes rapidly to form a mixture. Form AF. Then, as shown in FIGS. 8 and 9, the air-fuel mixture AF is moved upward by the piston 3 toward the top dead center by the piston 3 and the upper volume portion 4A of the combustion chamber 4 is discharged.
It is pushed up to the side and reaches the vicinity of the spark plug 9, thereby stratifying the air-fuel mixture.

According to the present embodiment configured as described above,
The following effects are obtained.

First, since the flat fuel spray F is injected substantially horizontally to the crown surface 3A of the piston 3 near the ignition timing, the crown surface 3A of the piston 3 and the wall surface of the cylinder head 2 are It is possible to supply fuel while ensuring a clearance to both sides, prevent wall flow and the like from occurring, and reliably realize stratification of the air-fuel mixture. That is, since the piston 3 rises in the vicinity of the ignition timing, when the fuel spray that spreads in a conical shape is injected by using the fuel injection valve 109 according to the conventional technique, this fuel spray causes this fuel spray to the crown surface 3A of the piston 3 and the cylinder head 2. However, in the present embodiment, since the flat fuel spray F is injected, the fuel is supplied by sewing the gap between the cylinder head 2 and the crown surface 3A of the piston 3. You can Then, in the vicinity of the ignition timing, the temperature of the compressed air is high, and the fuel spray F immediately vaporizes to form the air-fuel mixture AF, so that the fuel droplets are ignited.
It does not cause "fog" phenomenon or "smolder" phenomenon by adhering to.

Secondly, since the fuel injection is performed "near the ignition timing", it is possible to prevent the fuel spray F from diffusing and destroy the stratification, and to promptly vaporize the fuel. That is, for example, when fuel is sprayed during the intake stroke, there is a period between the time of fuel injection and the time of ignition, so if there is a tumble that vertically swirls in the cylinder 1, this tumble will make the air-fuel mixture uniform. However, it cannot be stratified. However, in the present embodiment, since the fuel is injected in the vicinity of the ignition timing, the fuel spray F regardless of the presence or absence of swirl (the flow that swirls in the cylinder 1 in the horizontal direction) or tumble.
The (mixture AF) is promptly pushed up to the vicinity of the spark plug 9 by the piston 3, and stable stratification can be realized. Conversely speaking, in the present embodiment, since the air-fuel mixture can be stratified without using the in-cylinder flow such as swirl and tumble, the structure such as the swirl control valve can be eliminated and the structure is relatively simple. Stable stratification can be realized at low cost.

Thirdly, the pair of injection holes 22 and 23 are arranged so that the line C--C connecting the centers of the outlets 22A and 23A is substantially perpendicular to the crown surface 3A of the piston 3, and each injection is performed. The injection axes X ₁ -X ₁ , X ₂ are arranged so that the fuel injected from the holes 22, 23 collides with each other at a point CP in the combustion chamber 4.
Since the fuel injection valve 10 having -X ₂ is used is used, the atomized flat fuel spray F that spreads in a substantially fan shape can be easily obtained, and is quickly vaporized to stratify the air-fuel mixture. Can be realized. That is, in this embodiment, since the fuel is injected near the ignition timing, the time margin until ignition is small, but since the atomization is promoted by utilizing the resonance phenomenon due to the collision of fuels, the inside of the combustion chamber 4 is In combination with the high temperature, the fuel spray F can be quickly vaporized to obtain the air-fuel mixture AF.

Fourth, the outlet portion 22 of each injection hole 22, 23
The ratio α of the square roots of the cross-sectional areas S ₁ and S ₂ of A and 23A is set to “1.
Since it is set to fall within the range of 25 to 3.50 ”, the fuel can be atomized by utilizing a stronger resonance phenomenon, and the vaporization can be promoted in combination with the temperature in the combustion chamber 4.

In the above embodiment, the preferable fuel injection valve 10 for obtaining the flat fuel spray has been described by taking the one shown in FIG. 4 as an example, but the present invention is not limited to this, and the flat fuel is also possible. As long as the fuel injection valve can inject the spray, other types of fuel injection valves such as a suckless hole type fuel injection valve and a so-called outward opening type fuel injection valve can be used. Further, in the above-described embodiment, the case where each of the injection holes 22 and 23 is formed into an elliptical shape is illustrated, but the present invention is not limited to this, and may be formed into another shape such as a perfect circle shape or a triangular shape. .

[0044]

As described in detail above, according to the direct injection type spark ignition internal combustion engine according to the present invention, the flat fuel spray is injected substantially horizontally to the crown surface of the piston in the vicinity of the ignition timing. Because of the configuration, the fuel can be supplied while ensuring the clearance between the crown surface of the piston and the wall surface of the cylinder head. As a result, while preventing the fuel droplets from adhering to the piston or the like to form a wall flow, it is possible to rapidly form the air-fuel mixture by using the high-temperature compressed air in the vicinity of the ignition timing. By pushing up to the cylinder head side by the piston, stratification of the air-fuel mixture can be realized.

The pair of fuel injection holes are arranged so that the line connecting the centers of their outlets is substantially perpendicular to the crown surface of the piston, and the injected fuel is injected so as to collide with each other in the combustion chamber. Since the configuration is such that the axis is set, it is possible to inject the atomized substantially flat fuel spray, which is atomized by utilizing the resonance phenomenon caused by the collision of fuels, substantially horizontally to the crown surface of the piston.

Further, since the square root ratio of the cross-sectional area of each injection hole outlet is set in the range of 1.25 to 3.50, the atomization is promoted by utilizing the stronger resonance phenomenon. Therefore, the fuel spray can be quickly vaporized, and the stratification of the air-fuel mixture before ignition can be realized more reliably.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing a main part of a direct injection type spark ignition internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a plan view showing the relationship between the shape of fuel spray and a spark plug or the like.

FIG. 3 is a vertical sectional view of fuel spray.

FIG. 4 is a sectional view showing a main part of a fuel injection valve.

FIG. 5 is a plan view of a nozzle member showing a positional relationship between each injection hole and a piston crown surface.

FIG. 6 is a characteristic diagram showing the relationship between the aperture ratio α and the strength of resonance.

FIG. 7 is a characteristic diagram showing the relationship between the aperture ratio α and the collision area ratio.

FIG. 8 is a diagram showing a state immediately before ignition in which a mixture is formed.
Explanatory drawing similar to FIG.

FIG. 9 is a plan view showing the relationship between the shape of the air-fuel mixture and the spark plug or the like.

FIG. 10 is a structural explanatory view showing a main part of a direct injection spark ignition type internal combustion engine according to a conventional technique.

[Explanation of symbols]

 2 ... Cylinder head 3 ... Piston 3A ... Crown surface 4 ... Combustion chamber 9 ... Spark plug 10 ... Fuel injection valve 11 ... Injection valve main body 22, 23 ... Injection hole 22A, 23A ... Injection hole outlet part

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area F02M 61/14 Z 61/18 320 A 360 J 69/04 Z

Claims (3)

[Claims] 1. A direct injection type spark provided with a fuel injection valve for injecting fuel into a combustion chamber formed between a cylinder head and a piston, and a spark plug for igniting an air-fuel mixture formed in the combustion chamber. An ignition internal combustion engine, wherein the fuel injection valve injects a flat fuel spray substantially horizontally with respect to the crown surface of the piston in the vicinity of ignition timing. organ. 2. The fuel injection valve includes an injection valve main body, and a pair of injection holes formed at a tip side of the injection valve main body,
The injection holes are arranged such that the line connecting the outlet centers of the injection holes is substantially perpendicular to the crown surface of the piston, and the injections are performed so that the injected fuels collide with each other in the combustion chamber. The direct injection spark ignition internal combustion engine according to claim 1, wherein the injection axis of the hole is set. 3. The fuel injection valve according to claim 2, wherein the ratio of the square roots of the cross-sectional areas of the outlets of the respective injection holes is set in the range of 1.25 to 3.50. Direct injection spark ignition internal combustion engine.